GREGORY: FISH SKULLS 



369 



The premaxillae have long ascending processes, which, as already stated, are received 

 by a diverging fossa above the mesethmoid ; the upper jaw must therefore be to some extent 

 protrusile. The opposite ascending processes of the premaxillse are closely appressed and 

 united by connective tissue. The articular processes of the premaxillse are expanded ovals, 

 much as in Uranoscopus. The maxillae have the proximal fork and rounded articular 



Fig. 248. Aslroscopus. Top view. 



processes, as in other derivatives of normal percoids. The olfactory chambers are very 

 small, squeezed in between the articular processes of the maxillae and the forwardly-displaced 

 flanges of the lateral ethmoids. The constriction of the olfactory chamber is primarily due 

 to the small size of the enclosed sensory capsule but the extreme forward displacement 

 of the small orbits has probably also contributed to it. The dorsal rim of the mouth has 

 been raised until it is level with the cranial table, while the premaxillae have, as it were, been 

 pushed back into the face. At the same time the quadrate-articular joint has been drawn 

 forward so as to be only a little way behind the strongly upturned mouth. As a result of 

 all this the mandible is inclined sharply upward, the palatopterygoid arcade is steeply 

 inclined. 



The head as a whole is very wide. Hence the opposite pterygo-metapterygoid tracts 

 are removed far from the mid-line and there are no mesopterygoids. The hyomandibulars 



